For the efficient screening of drugs of abuse, simple but unambiguous analytical methods are required which can be performed on-site. This project is designed to develop an immunosensor for the detection of drugs of abuse. While our project is focused on the detection of benzoylecgonine, the major urinary metabolite of cocaine, immomunosensor technology can be readily adapted to other substances for which antibodies are available, including therapeutic drugs and other physiologically active compounds. Operation of the immunosensor is a single-step procedure which does not require the usual steps associated with immonoassays such as pipetting, adding of reagents, manual separation and mixing; the disposable sensor need only be dipped into the biological medium (urine, blood, saliva). The signal generated will be monitored with existing technology that has been developed for the measurement of blood glucose. Once the sensor is dipped in the biological medium, the assay will be complete in a minimum of 3 to 10 minutes, without the need to stop the reaction when it is complete.